What is the volume in cubic cm of a pyramid whose area of the base is 25 sq cm and height 9 cm?
Aptitude
Volume and Surface Area
Difficulty: Easy
Choose an option
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A60
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B75
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C90
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D105
Answer
Correct Answer: 75
Explanation
### Concept & Volume of a Pyramid
The volume of any pyramid is one-third of the product of its base area and its perpendicular height, regardless of the shape of the base (square, triangular, etc.).
Volume Formula: $$V = \frac{1}{3} \times \text{Base Area} \times \text{Height}$$
### Step-by-Step Solution
1. Extract the given values from the problem:
Base Area ($A$) = 25 sq cm
Height ($h$) = 9 cm
2. Apply the volume formula for a pyramid:
$V = \frac{1}{3} \times A \times h$.
3. Substitute the given numbers into the formula:
$V = \frac{1}{3} \times 25 \times 9$.
4. Simplify the expression by multiplying $\frac{1}{3}$ with 9 first:
$V = 25 \times 3$.
5. Calculate the final result:
$V = 75$ cubic cm.
### Exam Strategy & Shortcut
You don't need to know what kind of polygon forms the base; the formula $V = \frac{Ah}{3}$ applies universally. Always look to divide the height by 3 first to make mental math trivial ($9/3 = 3$, $25 \times 3 = 75$).
### Common Pitfall
A common mistake is treating the pyramid like a prism and forgetting to divide by 3 (which would incorrectly yield 225).
### Final Answer
Therefore, the correct answer is **75**.